Method of evaporation and distillation of liquids.



C T. THORSSELL.

METHOD OF EVAPORATION AND DISHLLATION 0F LIQUIDS.

APPLICATION FILiD SEPI. 8. 1914.

1,204,716. Patented N0V.1-'1,1916.

I IN YEA/TUB 17 7 ATTORNEY UNITED STATES PATENT OFFIGE.

CARL THEODOB llIHOIIiSSELIi, OF GOTTENBDRG, SWEDEN.

METHOD OF EVAPORATION AND DISTILLATION F LlIQUIDS.

Specification of Letters Patent.

Patented Nov. 14, 1916.

Application flied September 8, 19M. Serial No. 860,707.

'I To all whom it may concern: Beit. known that I, CARL Txwonor THORS- BELL, a subject of the King of Sweden, re siding at Gottenborg, in the. county 7 of Mulmohus, Sweden, have invented certain new and useful Improvements in Methods of Evaporation and Distillation oflliquids,

of which the following is a specification.

This invention has for its object the evaporation and distillation of l quids.

In the evaporation, distillation and like treatment of-liquids the'greotest part of the I thestill is compresed to a pressure some- What higher than the pressure prevailing in the still so that the vapor will be condensed, whereupon it is brought into a heating apparatus in this -vessel, in which 'it square cm. is 1.20 cubic meters.

yields its best (of evaporation to the liquid to be distilled. Assuming that such an appara: tus evaporates 2000 kilograms of water per hour and the evaporated steam is compressed from one kg. per sq. cm. to 1.3 kg. pressure per square centimeter, the eompreisor must compress the'volume 2000 (1.67- 2):.940 cubic meters, since the volume of 1 kilogram of steam at a. pressure of 1.0 kg. per square cm. is 1.67cubic meters and the; volume of} 1 kg. of steam at a pressure off1.3 kg. per

I this compression be carried .out in a cylinder with a. cross-sectional, area. of 1 square meter, the piston must travel 940 meters; The pressure on the piston amounts to L3 10000 :13000 kg. Thus the work donenmounts to' 13000 940=12220000 kilogram-meters in an hounwhich corresponds to a power of 46 H. P. To obtain a better result it has been suggested thatLn calorific motor may bc'used r this compression and thnt the heat of its exhaust (gases may be used for preheating the liqui .to be distilled.

My invention relates to a method by means of which thecostzforthe compensa-,'

tion of theheigtof evaporation is eliminated in" a more eificlentway, by the use of means that require only a minimum ofpower. This result is obtained by carrying out the distillation at the critical temperature of the liquid inquestion or at a tem erature somewhat lower than the critical temperature.- As the heat of: evaporation at the critical point is :0, it is evidentlthut the compensation of this heat-and-thus the cost of the same are avoided.

For the sake of making the invention clear the new method applied to thedistillation of water-is hereinafter explained. The criti cal point of water is reached at s temperature of 374 Gels. and at a pressure of 217.5

atmospheres (224.24 kg. per square cm.) according to P/ryeikali-rck-Ghemisohe Tarbel- Zen, 1912, page 447, by Landolt-Bornstein (expfriments by Holborn and .Baiimann .1910 l Theinvention is illustratedby way of example in the accompanying drawing, which shows an apparatus for use in carrying out the invention.

As shown, the outlet pipe 2 leads from the distillation vessel 1 to a cooling coil 5 in a. vessel 4, the coil 5 being connected with the pump cylinder 7 by means'of a pipe 6. A'-

valve 3 in the pipe 2 is arranged in such a way that, it opens when a ccrtam'diiference of pressure is established. A valve 15 is arrahged in the pipe 6, and another valve .16 is arranged in the pipe 12 leading from. the

system. The inlet pipe 11 of the, system with the valve 18 is connected with a suction and compression pump 8 or. the like, the piston of which is driven from a driving gear or a motor 9 and also connected with the piston in another cylinder? or the'dike. A pipe 10 provided with a valve 17 leads from the pump cylinder 8 to the vessel 4 whichlatter is connected with the distillation vessel 1 by means of a pipe13- having a check valve 14.

The-vessel 1 isfilled with Water tain level and the valve 1'5 is closed. Heat is supplied to the vessel 1, whereby the pres sure is increased. When the pressure has risen to. that amount at which the valve 3 opens and which in what follows is assumed. tobe 3 kg. per square cm., the steam'passes over into the cooling coil 5. On account of the pressure decreasing ,when the steam.

passes through the valve ,3, the steam will be condensed to water in the'coil'li .(the Joule-Thomson e'flect). When the pressure in the vessel 1 has risen to 225 kg. per sq. cm. the critical point is passed and the temperoture is maintained at 374 C. Now a pressure of 225-3 222 kg. per square cm. prevails in the coil 5, but the Water here has not yet the temperature of steam at this pressure. If now the liquid is set in motion in the way hereinafter described, so that the water condensed in the coil 5 is drawn oft successively without the pressure in the coil being decreased, and it fresh water is pumped into the vessehl through the pipe 10, the vessel l, the pipe 13 and the check valve 14 which prevents a return flow, while the pressure and the tem icrature in the was sel 1. are maintained, then the temperature of the coil5 must in course reach the point required according to the physical laws;

According to the investigation of Davis (publications from Harvard University 1909) the Joule-Thomson effect, expressed in fall of temperature per fall of pressure of 1 kg. per square cm. for water is as follows: at 200 C.=2.2 C.; at 250 C.:l.5 0.; at 300 C.:1.l C. and at 360 (1:09

(J. From this one may come to the conclusion that the fall of temperature at 374 C. is 085 C. for a fall of pressure of 1 kg. per square cm. and thus 255 C. for a fall of pressure of 3 kg. per square cm. Thus the pressure and the temperature in the coil are respectively 222 kg. per square cm. and 3742.55::371.45 C. But the pressure of I saturated steam at a temperature of 371.455 I C. is 217.59 kg. per square cm., and consequently the water in the coil is liquid.

If the motion of the liquid be maintained in the manner described, 6. e.,,in such a way that the temperatures and pressures stated are not altered, the operation of the apparatus will result in the water .being distilled from the vessel 1, without consuming the quantity of heat corresponding to the heat of evaporation, and condensed into the coil 5.

In order to cause the water to pass into the vessel 1 it will be'requisite to force It in, at a. pressure higher than 225 kg. er

sqiiare cm. To this end a rather consi erable amount of work ought tobe required, but in order to avoid this additional work as far as possible, or in a part of the water that is condensed in the coil 5 at a pressure of square cm. is utilized. -For this purpose the following device may be used: By connecting the two pistons in the cylinders .7 L and 8 with a common piston rod the pressure on the piston in the cylinder. 8 may be anced by means of the piston in the cylinder 7. If water of a pressure of 222 kg. per 'p square cm. is admitted through the valve 15, while the. valve 16 is closed, and the power required for compensating the difl'erence of pressure between the pipe 10 (227 kg: per square cm. and the cylinder 7 (222 kg. per square cm. is supplied by the motor 9, then the piston in the pump will move forward the energy in the water.

222 kg. per

bal-

but the valves 18 and 16 opened. The water is drawn into the cylinder 8 through the valve 18 and it is drawn oil the balancing cylinder 7 through the valve 10.

The newly admitted water absorbs heat from the water in the coil 5 on its passage through the vessel 4 so that the water in the coil attains a temperature of 30 C. when it is drawn off. The )ressure' in the coil 5 falls by this fall 0 temperature so very little that it need not be taken into consideration. According to Thomsonsformula, for which see Chwvolson, Lehrbueh der Physils, vol. 3, page 562 (Brunswick, 1905) 5 Drecker: Wieclermamis Annalee, vol. 20, p. 870 (1883) Joule: Phi-Z. Transact, vol. 149, p. 133 (1859); Phil. Mag. (4), vol. 15, p. 17 (1858,); Burton and Marshall: Proc. R. Soc. vol. 50, p. .130 (1891), for the calculation of increase in temperature by the com pression of liquids this increase is as folows:

e =10333 T' a A equals the mechanical equivalent of lent alpha is the increase in volume corresponding to a rise in temperature of one degree. V is the volume at 0. C, is the thermal capacity at constant pressure.

In this formula as appears in the numerator of the fraction and thus 9 is proportional to this quantity. For water between 200 and 500 atmospheres a=about 10*)(600 (Chwolson Lehrbuch der Phystk, band 3, page 562). This is confirmed by the experiments of Joule with compression of water at +30 C. and 26.19 atmospheres when the increase in temperatures amounted to 0.05%" C.

If'the' apparatus be worked in the man ner described, the amount of heat and power required is as follows: when the apparatus is running: If the vessel 4 and the coil 5,.

are constructed and dimensioned according that the water leaves the coil 5 with a temperature of +30 C. and the water forced into the vessel 4 by means of the pumgi 8 has a temperature of +15 C., while the quantity water passing through the apparatus er hour amounts to 2000 kilograms, then the quantity of heat required for heating 2000 kilograms of water from 15 to 374 C. amounts to 2000(374-'15)=718000 calories. The water in the coil 5 delivers to the water in the z-mr'roundir igl vessel 2000 (371--30) 68 2000 calories. us, in order'to maintain the temperature in the vessel 1, it is necessary to supply 718000682000:36000 calories per hour, this constitutin the theoretical amount of heat required ihr the apparatus.

millimeters. The pressure on this area =5.52 5:27.6 kilograms which must he covered by the motor 9. This corresponds to an amount of work 27.6 kilogrammeters, 21. 6.

constituting the theoretical amount of power required for the apparatus.

It is evident that the heat in the distilled water or a part thereof in some cases also may he used for purposes other than for heating the freshly admitted liquid, and also that its pressure may be used for other purposes. A part of the distilled liquid may also be used for forcing more liquid into the distillation vessel.

In some cases the distillation may be carried out at a temperature that is somewhat lower than the critical temperature.

Having now particularly described and ascertained the nature of my said invention and in what manner the same is to be performed, I declare that what I claim is 1. A method of evaporation and distillation of liquids characterized by carrying out the evaporation or distillation at the pressure and temperature corresponding to or near the critical point of the liquid, as and for the purpose specified.

A method of evaporation and distillation of liquids consisting in generatin the vapor at or near the critical point 0 the liquid and exposing the vapor, when leaving the distillation vessel, to a. small fall of pressure and temperature in such manner that the vapor is condensed, i. e., so that its pressure becomes higher than the pressure corresponding to the pressure of saturated vapor at the prevailing temperature.

I. A method of evaporation and distillation of liquids, consisting in generatin the vapor at or near the critical point 0 the liquid and conducting the liquid to be distilled in such a path to the distillation vessel that it may receive heat from the liquid already distilled, in order that this heat or a part thereof may be used to bring more liquid to the critical point.

4. A. method of evaporation and distillation of liquids, consisting in generatin the vapor at or near the critical-point o the liquid and using the distilled liquid, still under high pressure, or a part thereof as motive fluid for forcing more liquid into the vessel in which the distillation takes place.

5. A methodof evaporation and distillation of liquids, consisting in generatin the vapor at or near the critical point 0 the liquid and causing the liquid to be distilled to pass the liquid already distilled by means of the pressure of the latter liquid in such a path that it becomes heated before it is forced into the vessel (1), in order that both the pressure and the heat of the liquid distilled may be utilized.

In testimony whereof I have aflixed my signature in presence of two witnesses.

CA RL TIHIODOR THORSSELL.

Witnesses A. W. ANDERSON, T. G. BBANZELLY. 

